Your sponsorship page says SOLD OUT by one or more of your sponsorships, but you wish to sell more of these sponsorship packages.
Goto Sponsors -> Sponsorships, under Action, Settings set Total Available for the sponsorship in question to 1 or more. The system will keep track of sponsorships sold and only sell the available quantity, if this field is used. This is an optional field, and you can leave it blank for unlimited sales. If the Total Available is set to 0, it will display as SOLD OUT and cannot be ordered online.